Critical Molecular Weight Effects in the Aggregation of Phospholipid Vesicles Triggered by Water-Soluble Polymers and an Integrated Glycolipid

Takeoka, Shinji; Sou, Keitaro; Arase, Shinya; Ohgushi, Takeru; Tsuchida, Eishun

doi:10.1021/ma961064q

Cited by 5 publications

(6 citation statements)

References 31 publications

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“…The solutions of PEG with different molecular weights were added to the dispersion of the phospholipid vesicles with 0.2 mol % PEG−lipids on the surface for the study of the M c for the aggregation of the vesicles. The larger M c indicates the higher dispersion stability of the vesicles because of the restriction of the interaction between the vesicular surface and the added polymers . The M c of the phospholipid vesicles (DPPC/cholesterol/DPPG = 5/5/1 m/m) without PEG modification is 1000, and that with PEG50−DSPE has an M c of 12 000.…”

Section: Resultsmentioning

confidence: 99%

“…We added a solution of the PEGs (500 μL, 0.15 kg dm -3 ) to the vesicle dispersion (2 mL, 1.39 mM) in a cuvette ( l = 1 cm) at 37 °C. The turbidity change (ΔOD) at 600 nm was monitored 15 min after the addition of PEGs with a UV−vis spectrophotometer (MPS-2000, Shimadzu Co.) . The M c was determined as the minimum molecular weight of the PEGs for the initiation of turbidity increase.…”

Section: Methodsmentioning

confidence: 99%

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Synthesis and Assembly of Poly(ethylene glycol)−Lipids with Mono-, Di-, and Tetraacyl Chains and a Poly(ethylene glycol) Chain of Various Molecular Weights

et al. 2000

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We synthesized a series of amphiphiles with poly(ethylene glycol) [MW 2000 (PEG20), 5000 (PEG50), 12 500 (PEG125)] as a headgroup and one, two, or four palmitoyl chains (1C16, 2C16, or 4C16), using a lysine monodendron as a connector. The relationship between the hydrophilic−hydrophobic balance of the multiacyl PEG-lipids and the physicochemical characteristics in self- or co-assembly with phospholipids were studied. The PEG-lipids were easily synthesized by combination of a general liquid-phase peptide synthesis and the acylation of an amino acid. The PEG part of the PEG−lipid films was crystallized to show a typical spherulite pattern. The thermal properties and microscopic observation revealed the phase separation of PEG and acyl chain parts. The critical micelle concentrations (cmcs) mainly depend on the number of acyl chains rather than the molecular weight of the PEG chain, although the area per molecule is dependent on the molecular weight of the PEG chain rather than the number of the acyl chains. The gel-to-liquid crystalline phase transition temperature was increased with the increasing number of acyl chains and the decreasing molecular weight of the PEG chain. The PEG−lipids in the aqueous dispersions assemble to take fibrous structures with bimolecular thickness because of the intermolecular hydrogen bonding. The PEG−lipids were immobilized onto the surface of the phospholipid vesicles by simply adding their aqueous dispersions to the vesicle dispersion; however, they dissociated from the vesicles on dilution of the mixed dispersion because they were incorporated into the vesicles in an equilibrium state. To prevent the dissociation of the PEG−lipids, at least two and four acyl chains were required for PEG with M w 5000 and 12 500, respectively. The aggregation of the vesicles by the addition of water-soluble polymers was significantly inhibited with the increasing molecular weight of the PEG chain. For the tight immobilization of the PEG−lipids with the long PEG chain onto the vesicular surface, an increased number of acyl chains is necessary, and the surface modification with the long PEG chains significantly increases the dispersion stability of the vesicles.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Synthesis and Assembly of Poly(ethylene glycol)−Lipids with Mono-, Di-, and Tetraacyl Chains and a Poly(ethylene glycol) Chain of Various Molecular Weights

et al. 2000

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“…The turbidity change (∆OD) at 600 nm was monitored for 15 min after the addition of PEG by a UV-vis spectrophotometer (Shimadzu, MPS-2000). The minimum molecular weight of added PEG for the aggregation of the vesicles was defined as a critical molecular weight (M c ) (20).…”

Section: Critical Micelle Concentration (Cmc)mentioning

confidence: 99%

“…The incorporated amount of PEG-lipids was easily controlled by varying the added amount of PEGlipids. Phospholipid vesicles tend to aggregate in the presence of water-soluble polymers by molecular interaction (20). Because the dissociation process of the absorbed polymer from the surface of the vesicle is dominant in this interaction, the molecular weight of the polymers should represent the degree of interaction between the polymer and the surface of the vesicle.…”

Section: Stability Of the Vesicle Dispersionsmentioning

confidence: 99%

Poly(ethylene glycol)-Modification of the Phospholipid Vesicles by Using the Spontaneous Incorporation of Poly(ethylene glycol)-Lipid into the Vesicles

et al. 2000

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The critical micelle concentrations of 1, 2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[monomethoxy poly(ethylene glycol) (5000)] (PEG-DPPE) and its distearoyl analogue (PEG-DSPE) were 70 and 9 microM, respectively, in buffer solutions ([Tris] = 20 mM, [NaCl] = 140 mM, pH 7.4) at 37 degrees C. When these PEG-lipid micelle dispersions were mixed with the dispersions of phospholipid vesicles comprised of a C16 membrane, of which the carbon number is 16, or a C18 membrane, the PEG-lipid micelles were dissociated into monomers and then spontaneously incorporated into the surface of the preformed vesicles. The incorporation rates and the enthalpy changes during incorporation were measured with an isothermal titration microcalorimeter. The incorporation rate of PEG-DPPE was faster than that of PEG-DSPE, because the dissociation rate of the PEG-DPPE micelles was faster than that of PEG-DSPE micelles. The incorporation equilibrium constant of PEG-DSPE was larger than that of PEG-DPPE due to its slow dissociation rate from the membrane, caused by the stronger hydrophobic interaction. The combination of PEG-DSPE and the C18 membrane was the most thermodynamically stabilized pair. Furthermore, the dispersion stability of the surface-modified vesicles prepared by this spontaneous incorporation was analyzed by using the critical molecular weight of the polymer for the aggregation of vesicles. The aggregation of the vesicles was successfully supressed with an increase in the molecular weight of the PEG in the PEG-lipid and its incorporation ratio.

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“…We selected Dex instead of PEG because it was reported that the association of plasma proteins is enhanced by PEG (45 -47) due to the excluded volume effect, but not with Dex (48). It has been established in our laboratory that the critical molecular weight of Dex required to induce aggregation is approximately 15 kDa, and complete aggregation requires a molecular weight higher than 100 kDa (36). It has been established in our laboratory that the critical molecular weight of Dex required to induce aggregation is approximately 15 kDa, and complete aggregation requires a molecular weight higher than 100 kDa (36).…”

Section: Discussionmentioning

confidence: 99%

Pretreatment of Serum Containing Hemoglobin Vesicles (Oxygen Carriers) to Prevent Their Interference in Laboratory Tests

Sakai¹,

Tomiyama²,

Masada³

et al. 2003

Clinical Chemistry and Laboratory Medicine

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Hemoglobin vesicles (HbV, diameter: 251 +/- 81 nm) are artificial oxygen (O2) carriers encapsulating concentrated hemoglobin (Hb) solution with phospholipid bilayer membrane, and their O2 transporting ability in vivo has been extensively studied. It is important to clarify the interference of the HbV suspension in clinical laboratory tests performed on serum and to establish a pretreatment method to avoid such an interference. The HbV suspension, acellular Hb solution ([Hb] = 10 g/dl) or saline, was mixed with a pooled human serum at various ratios up to 50 vol% ([Hb] = 5 g/dl), and the magnitude of the interference effect of HbV and Hb on 30 analytes was studied. The mixture of the HbV suspension and serum was ultracentrifuged (50,000 g, 20 min) to remove the HbV particles as precipitate, and the supernatant was analyzed and compared with the saline control group. The HbV particles were also removed by centrifugation (2,700 g, 30 min) in the presence of dextran (Mw 200 kDa). The HbV suspension showed considerable interference effects in most analytes. The majority of these effects was more serious than those of the acellular Hb solution. These findings are thought to be due to the light absorption of Hb in HbV and/or the light scattering generated in the suspension that interferes with the colorimetric and turbidimetric measurements. The components of HbV may also interfere with the chemical reactions of the studied assays. However, removal of the HbV from the supernatant diminished the interference in most of the assays: this is an advantage of HbV in comparison with acellular chemically modified Hb solutions.

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Critical Molecular Weight Effects in the Aggregation of Phospholipid Vesicles Triggered by Water-Soluble Polymers and an Integrated Glycolipid

Cited by 5 publications

References 31 publications

Synthesis and Assembly of Poly(ethylene glycol)−Lipids with Mono-, Di-, and Tetraacyl Chains and a Poly(ethylene glycol) Chain of Various Molecular Weights

Synthesis and Assembly of Poly(ethylene glycol)−Lipids with Mono-, Di-, and Tetraacyl Chains and a Poly(ethylene glycol) Chain of Various Molecular Weights

Poly(ethylene glycol)-Modification of the Phospholipid Vesicles by Using the Spontaneous Incorporation of Poly(ethylene glycol)-Lipid into the Vesicles

Pretreatment of Serum Containing Hemoglobin Vesicles (Oxygen Carriers) to Prevent Their Interference in Laboratory Tests

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